Methods of forming 3-D circuits with integrated passive devices

ABSTRACT

Methods of forming 3-D ICs with integrated passive devices (IPDs) include stacking separately prefabricated substrates coupled by through-substrate-vias (TSVs). An active device (AD) substrate has contacts on its upper portion. An isolator substrate is bonded to the AD substrate so that TSVs in the isolator substrate are coupled to the contacts on the AD substrate. An IPD substrate is bonded to the isolator substrate so that TSVs therein are coupled to an interconnect zone on the isolator substrate and/or TSVs therein. The IPDs of the IPD substrate are coupled by TSVs in the IPD and isolator substrates to devices in the AD substrate. The isolator substrate provides superior IPD to AD cross-talk attenuation while permitting each substrate to have small high aspect ratio TSVs, thus facilitating high circuit packing density and efficient manufacturing.

RELATED APPLICATION

This application is a divisional of co-pending U.S. patent applicationSer. No. 12/277,519, filed on Nov. 25, 2008.

FIELD OF THE INVENTION

The present invention generally relates to electronic devices andintegrated circuits (ICs) and their methods of manufacture, and moreparticularly, structures and methods for (3-D) integrated circuits (ICs)incorporating integrated passive devices (IPDs).

BACKGROUND OF THE INVENTION

As modern electronic devices, especially integrated circuits (ICs),become more complex there is a great need to extend circuit integrationinto three dimensions. This is especially true of devices and circuitsthat operate at high frequencies where there is often a need to includeintegrated passive devices (e.g., inductors, capacitors, resistors,transmission lines, ground planes, shielding structures, baluns, etc.)that cannot easily be provided as a part of the associated semiconductordevices. Accordingly, such integrated passive devices (IPDs) are oftenformed in dielectric and metal layers above the semiconductor substratein or on which the active devices, e.g., transistors of various kinds,are formed. (As used herein, the term “transistor” singular or plural,is intended to include any type of semiconductor device having two ormore terminals.) The greater the number and complexity of the integratedpassive devices (IPDs), the greater the need to extend the integratedcircuit structure into the third dimension perpendicular to the surfaceof the underlying semiconductor devices. Such devices and circuits arereferred to as “3-D integrated circuits” or “3-D ICs”.

Creating effective 3-D ICs incorporating high frequency power amplifiershas proved especially difficult because of electromagnetic (EM)cross-talk among the various components and higher than desired lossesarising from stray electromagnetic (EM) fields inducing undesirable eddycurrents in underlying semiconductor substrates. These effects can limitthe gain and efficiency of high frequency power amplifiers. Theseeffects are especially pronounced with advanced LDMOS (laterallydiffused metal oxide semiconductor) integrated power amplifiers thatemploy high resistivity (e.g., semi-insulating) substrates. The thickerthe substrate the greater the decoupling and the higher the qualityfactor Q of the associated integrated passive devices (IPDs). Thequality factor Q is a measure of the energy stored divided by the energydissipated per cycle by a resonant element, such as for example (but notlimited to) an inductor. However, use of thicker substrates createsother problems, such as for example, increased thermal impedance betweenpower amplifier active device (AD) regions on or near a front face ofthe substrate and a heat sink coupled to a rear face of the substrate.This increased thermal impedance can degrade overall performance. Thus,power amplifier ICs embodying IPDs involve conflicting requirements. Forexample, active device (AD) performance is generally optimized by usingthinner substrates for efficient heat extraction, while integratedpassive device (IPD) performance is generally optimized by using thickersubstrates. 3-D integration attempts to avoid this conflict by movingthe IPDs to layers above the active devices. However, there are physicallimits on the number and thickness of multilayer dielectric-metal stacksfor IPDs that can be deposited on a semiconductor substrate containingactive devices (ADs). This can make it difficult or impossible, forexample, to reduce the cross-talk among the IPDs and/or between the IPDsand the underlying ADs and their substrate. Thus, a need continues toexist for improved 3-D IC structures and methods where undesirableelectromagnetic cross-talk and thermal impedance effects aresimultaneously minimized or avoided. This is especially true in the caseof high frequency power amplifiers where cross-talk, thermal impedanceand other present day limitations are acutely felt.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and wherein:

FIG. 1 is a simplified schematic cross-sectional view of a generalized3-D IC comprising an active device (AD) chip, an isolator chip and anintegrated passive device (IPD) chip, coupled by conductive vias,according to an embodiment of the present invention;

FIG. 2 is a simplified schematic cross-sectional view of a generalized3-D IC comprising an active device (AD) chip, an isolator chip and anintegrated passive device (IPD) chip, coupled by conductive vias,according to a further embodiment of the present invention;

FIG. 3 is a simplified plan view of a typical through-substrate-via(TSV) employed in various embodiments of the present invention; and

FIGS. 4-16 are simplified schematic cross-sectional view of ageneralized wafer or chip in which a through-substrate-via (TSV) isbeing formed and interconnected to provide a 3D-IC, during variousstages of manufacture according to still further embodiments of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, or the following detailed description.

For simplicity and clarity of illustration, the drawing figuresillustrate the general manner of construction, and descriptions anddetails of well-known features and techniques may be omitted to avoidunnecessarily obscuring the invention. Additionally, elements in thedrawings figures are not necessarily drawn to scale. For example, thedimensions of some of the elements or regions or layers in the figuresmay be exaggerated relative to other elements or regions or layers tohelp improve understanding of embodiments of the invention.

The terms “first,” “second,” “third,” “fourth” and the like in thedescription and the claims, if any, may be used for distinguishing amongsimilar elements and not necessarily for describing a particularsequential or chronological order. It is to be understood that the termsso used are interchangeable under appropriate circumstances such thatthe embodiments of the invention described herein are, for example,capable of operation or fabrication in sequences other than thoseillustrated or otherwise described herein. Furthermore, the terms“comprise,” “include,” “have” and variations thereof, are intended tocover non-exclusive inclusions, such that a process, method, article, orapparatus that comprises a list of elements or steps is not necessarilylimited to those elements or steps, but may include other elements orsteps not expressly listed or inherent to such process, method, article,or apparatus. The term “coupled,” as used herein, is defined as directlyor indirectly connected in an electrical or non-electrical manner.

As used herein, the term “semiconductor” is intended to include anysemiconductor whether single crystal, poly-crystalline or amorphous andto include type IV semiconductors, non-type IV semiconductors, compoundsemiconductors as well as organic and inorganic semiconductors. Further,the terms “substrate” and “semiconductor substrate” are intended toinclude single crystal structures, polycrystalline and amorphousstructures, thin film structures, layered structures as for example andnot intended to be limiting, semiconductor-on-insulator (SOI)structures, and combinations thereof. The term “semiconductor” isabbreviated as “SC.” Unless otherwise specifically noted, the term“oxide” is intended to include any form of insulating dielectric whetherorganic or inorganic, and the terms “metal,” “metal layers,”“metallization” and “metallization layers” are intended to include anytype of electrical conductor, whether organic or inorganic, metallic ornon-metallic. Non-limiting examples of such conductors are dopedsemiconductors, semi-metals, alloys and mixtures, combinations thereof,and so forth. For convenience of explanation and not intended to belimiting, semiconductor devices and methods of fabrication may bedescribed herein for silicon semiconductors but persons of skill in theart will understand that other semiconductor materials can also be used.

Attempts have been made in the past to mitigate cross-talk problems byforming the IPDs on a separate fully optimized substrate, therebycreating an “IPD chip” that is vertically stacked on top of the activedevice (AD) substrate (an “AD chip”), and electrically coupling the twochips so as to tie the passive and active devices together in thedesired manner. It is this integrated coupling of the optimized IPD andAD chips that has proved to be especially difficult. If wire bonding orsolder bumps or other typical “back-end” manufacturing techniques areused, the advantages of advanced batch wafer processing are often lost.It is known to use conductor filled vias through SC wafers and othersubstrates as a means of providing electrical and thermal connectionsbetween the front and rear surfaces of the wafer or substrate andvarious components thereon. These are referred to as“through-semiconductor-vias” or “through substrate vias”, abbreviated as“TSVs”. Thus, TSVs could be used to couple IPDs on the front surface ofan IPD chip to the rear surface of the IPD chip where they could becoupled to matching connections on an underlying active device (AD)chip, using batch fabrication techniques. However, the availablemanufacturing technology for forming TSVs creates several design andmanufacturing conflicts that must be overcome to obtain space efficientchips and cost-effecting manufacturing. These have to do with therelationship between wafer thickness and TSV size and ease of formation.The thicker the wafer, the more difficult it is to form small area, highaspect ratio (AR) TSVs. The aspect ratio (AR) is given by the TSV depthd divided by the TSV width w, that is AR=d/w. Comparatively thick IPDwafers are desirable in order to minimize cross-talk to the underlyingAD wafer or chip and to minimize breakage during manufacturing. (It iswell known that thin wafers or substrates have higher manufacturingbreakage rates.) If, for these reasons, thicker IPD wafers or substratesare used, the TSVs have lower ARs and larger areas, thereby resulting ingreater overall chip area and higher cost for the same functionality.This is undesirable. Thus, there is a need for structures andmanufacturing methods that avoid the conflict between IPD wafer orsubstrate thickness and TSVs aspect ratio and lateral size.

In connection with the figures that follow, the terms “wafer” and“substrate” are used interchangeably. Further, in describing how thevarious elements making up a 3-D IC are fabricated, it is understoodthat during manufacture a “substrate” or “wafer” may contain many“chips” that are being formed simultaneously and that will eventually beseparated into individual components or integrated circuits. The 3-D ICsdescribed herein comprise several stacked chips interconnected via TSVs.They may be assembled (stacked and interconnected) while still in waferform and the stacked wafers then singulated into the individual 3-DIC's, or the individual chips making up the 3-D ICs may be firstsingulated from their parent wafers before being stacked andinterconnected in chip form to provide the 3-D ICs. Additionally,singulated chips can be stacked on an un-singulated wafer in achip-on-wafer integration arrangement. The bottom wafer is then latersingulated for form the 3-D ICs. All of these arrangements are useful.Thus, even though elements making up various levels of the 3-D IC may bereferred to as “chips” or “substrates” or “wafers” in describing themanufacturing process, they remain in wafer form until ready to bestacked and interconnected and can be stacked and interconnected beforeor after singulation.

FIG. 1 is a simplified schematic cross-sectional view of a portion ofgeneralized 3-D integrated circuit (IC) 18 comprising integrated passivedevice (IPD) chip 340 having IPD substrate 34 with IPD zone 38 thereon,isolator chip 300 having isolator substrate 30 and active device (AD)chip 200 having active device (AD) substrate 20, stacked one upon theother and coupled by conductive vias (i.e., TSVs) 40, according to anembodiment of the present invention. IPD zone 38 is the region of 3-D IC18 in which the passive components are primarily located. In variousimplementations IPD zone 38 can comprise various metal, dielectric andother layers arranged to provide, for example and not intended to belimiting, inductors, capacitors, interconnections, resistors,transmission lines, couplers, splitters, baluns, and/or other well knownpassive components. For the purposes of the present invention it isassumed that IPD zone 38 can contain integrated passive devices (IPDs)of various kinds. The present invention does not depend on the exactnature of these integrated passive devices (IPDs).

With respect to the TSVs, the reference number 40 is used to refer toTSVs generally. The convention is adopted of identifying the TSVs withineach substrate by adding the substrate reference number, whereby TSVs4020 refer collectively to those TSVs passing through substrate 20, TSVs4030 refer collectively to those TSVs passing through isolator substrate30, and TSVs 4034 refer collectively to those TSVs passing through IPDsubstrate 34. Reference numbers 401 through 407 refer to TSVs that arecoupled so as to pass through several levels of 3-D IC 18. For example,TSV 401 at the left of 3-D IC 18 (and TSV 402 at the right of 3-D IC 18)has a TSV segment within AD substrate 20 that is coupled to a TSVsegment above it passing through isolator substrate 30 that is in turncoupled to a further TSV segment above it within IPD substrate 34, so asto provide electrical continuity extending from IPD zone 38 on top ofIPD substrate 34 to lower surface 23 of AD substrate 20. Analogously,TSVs 403-407 extend from IPD zone 38 to AD interconnect zone 26,providing electrical continuity therebetween. In a preferred embodimentIPD substrate 34 and the isolator chip substrate 30 will both be highresistivity semiconductors. For example if the substrates are formed ofsilicon, the resistivity in this preferred embodiment will be 1000ohm-cm or higher. Thickness 35 of the IPD substrate 34 typically will bebetween 10 and 200 micrometers or larger and preferably between 40 and100 micrometers. Thickness 31 of the isolator chip substrate 30typically will be between 10 and 200 micrometers or larger andpreferably will be between 40 and 100 micrometers. The TSVs illustratedin FIG. 1 are intended to merely be examples of TSVs extending throughvarious layers of the third dimension of a 3-D IC and not to be limitedmerely to what is shown. Persons of skill in the art will understandbased on the description herein, that TSVs can be arranged to penetrateany combination of the various superposed layers or regions of any 3-DIC and that they need not be all arranged vertically one above the otheras illustrated herein but can be off-set by providing horizontal metalleads coupling a TSV in a higher layer to an off-set TSV in a lowerlayer at an interface between superposed layers or regions (e.g., seeFIG. 2).

Active device (AD) substrate 20 of thickness 21, with upper surface 22and lower surface 23 has, in this example, active devices locatedgenerally in zone 24 proximate upper surface 22, but in otherembodiments, the active devices may be distributed more generallythrough substrate 20. Such active devices can include any kind oftransistor(s) and such associated passive devices as are incorporatedwithin or on substrate 20, using means well known in the art, and theterm “active devices” and the abbreviation “AD” are intended to beinclusive of such other elements. The present invention does not dependupon the particular type or types of active devices included insubstrate 20. Substrate 20 generally comprises a semiconductor in whichthe active devices are formed. Silicon is a non-limiting example of asuitable semiconductor for substrate 20, but other semiconductormaterials may also be used. As noted earlier, LDMOS power amplifiers arenon-limiting examples of the kinds of devices that can be used in activedevice (AD) zone 24 of substrate 20, in which case, it is desirable thatsubstrate 20 be of a semi-insulating semiconductor material, e.g., of aresistivity equal or greater than about 1000 ohm-cm. However, in otherintegrations, an LDMOS substrate may have a lower resistivity, forexample and not intended to be limiting, in the range of 10 milliohm-cmto 10 ohm-cm. In yet other applications, active device substrate 20 mayhave a different resistivity as appropriate for formation of the activesdevices in the AD zone 24. For example, the resistivity of active devicesubstrate 20 may typically be of the order of about 10 ohm-cm for asilicon CMOS (complementary metal oxide semiconductor) AD substrate 20.In general, it is desirable that substrate 20 be significantly thinnerthan substrates 30 and/or 34, to facilitate heat removal from activedevice region 24 while at the same time providing good RF isolationbetween IPD zone 38 and AD interconnect zone 26 and device region 24 ofsubstrate 20. In these circumstances it is desirable that thickness 31of isolator substrate 30 and/or thickness 35 of IPD substrate 34 be inthe range of at least about 2 to 20 times thickness 21 of AD substrate20, more preferably at least about 5-15 times thickness 21 andpreferably at least about 10 times thickness 21 of substrate 20.

In a preferred embodiment, active device (AD) interconnect zone 26 ofthickness 27 is desirably provided on upper surface 22 of AD substrate20. AD interconnect zone 26 may comprise only a single level ofmetallization or include multilayers of metallization. Its purpose is toconnect the various devices included in AD substrate 20 to each otherand to some or all of conductive vias 40 that extend to higher regionsof 3-D IC 18 and/or to lower surface 23 of AD substrate 20, the detailsof which will depend upon the particular electrical function beingprovided. It is assumed that the active devices included in region 24 ofsubstrate 20 will have contact regions on surface 22 to which thevarious metal leads provided in AD interconnect zone 26 are coupled.Such contact regions are routinely provided for semiconductor devicesand integrated circuits. However, in other embodiments, conductive vias40 may be coupled directly to such contact regions and AD interconnectzone 26 may be omitted or only have a single metal level, depending uponthe IC function that is being implemented. Thickness 21 of AD substrate20 can therefore be optimized (e.g., made much thinner) to facilitateefficient heat removal. As will be subsequently explained, themanufacturing methods described herein facilitate providing thinsemiconductor substrates having space-efficient (small area) TSVstherein while avoiding the higher breakage rates during manufacturingusually associated with thin substrates.

Isolator substrate 30 has thickness 31, upper surface 32 and lowersurface 33 and includes TSVs 4030 aligned either with one or more ofTSVs 4020 of substrate 20 (as for example for TSVs 401, 402) and/or withcontact regions of AD interconnect zone 26 and IPD zone 38 (as forexample with TSVs 403-407). Among other things, a purpose of isolatorsubstrate 30 of thickness 31 is to provide adequate separation betweenIPD zone 38 and AD interconnect zone 26 and/or substrate 20 so as tomitigate or eliminate stray electromagnetic coupling (e.g., cross-talk)between IPD zone 38 and AD interconnect zone 26 and/or substrate 20 withdevice layer 24, while still allowing IPD substrate 34 to besufficiently thin so that high aspect ratio TSVs can be formed therein.Stated another way, isolator substrate 30 allows the TSV formation andIPD substrate thickness to be simultaneously optimized without conflict.

For example, suppose that distance 42 between IPD zone 38 and ADinterconnect zone 33 (or substrate 20) needs to be equal to twicethickness 35 of IPD substrate 34 in order to sufficiently attenuatestray electromagnetic fields generated in IPD zone 38 so that cross-talkis minimized. If one attempts to achieve this by doubling the thicknessof IPD substrate 34, it becomes extremely difficult to efficientlyfabricate TSVs 4034 through IPD substrate 34. The aspect ratio of suchdouble-depth TSVs will be much lower, the area of each such TSV must besubstantially larger and they must be placed further apart. As aconsequence, the packing efficiency of the 3-D IC would be significantlydegraded and the overall fabrication time would be greatly increased (ittakes much longer to fill deep vias with conductors). Thus, the desireddesign and cost objectives may be unreachable with such an approach.These problems are avoided by providing isolator substrate 30 betweenIPD substrate 34 and AD interconnect zone 26 and underlying AD substrate20. Thickness 31 of substrate 30 plus thickness 35 of IPD substratetogether provide the total separation 42 that is needed for avoiding theunwanted EM coupling. At the same time, thickness 35 and thickness 31can both be in the zone where small diameter high aspect ratio TSV canbe easily and efficiently fabricated, thus preserving the desired ICpacking density. IPD substrate 34 having thereon IPD zone 38 is bondedto isolator substrate 30 such that the desired ones of TSVs 4034 and4030 are aligned and connected. Thus, separation 42 needed to reduce EMcoupling is achieved while still being able to provide the neededelectrical continuity between passive devices in IPD zone 38 and theconductors in AD interconnect zone 26 and devices in underlying ADsubstrate 20. This is a significant advance over the prior art.

FIG. 2 is a simplified schematic cross-sectional view of a portion ofgeneralized 3-D integrated circuit (IC) 18′ comprising integratedpassive device (IPD) chip 340′ having IPD substrate 34′ with IPD zone 38thereon, isolator chip 300′ having substrate 30′ and active device (AD)chip 200, stacked one upon the other and coupled by conductive vias(i.e., TSVs) 40, according to a further embodiment of the presentinvention. Like reference numbers are used to identify similar elementsin FIGS. 1 and 2 and primes (′) are added to the reference numbers ofsome otherwise analogous elements (e.g., 30 and 30′; 300 and 300′; 42and 42′, etc.) that differ somewhat in the embodiment of FIG. 2. Thediscussion of FIG. 1 is incorporated herein by reference. 3-D IC 18′ ofFIG. 2 differs from that of FIG. 1 by inclusion of further interconnectzone 44 of thickness 45 between substrate 30′ and IPD substrate 34′ ofIPD chip 340′. Thickness 42′is the sum of thicknesses 31, 45 and 35.Further interconnect zone 44 is created in the same general manner as ADinterconnect zone 26, except that it can provide lateral connectionbetween some of TSVs 4030′ and other of TSVs 4034′ that are notvertically aligned. While it is possible to form further interconnectzone 44 on the bottom of IPD substrate 34′, in a preferred embodiment,further interconnect zone 44 is desirably formed on top of substrate 30′of isolator chip 300′. For example, TSV 408 in isolator substrate 30′couples contacts in AD interconnect zone 26 (and/or underlying devicesin substrate 22) to horizontal conductor 46 in further interconnect zone44, which in turn is connected to TSV 409 in IPD substrate 34′ that iscoupled to contacts in overlying IPD zone 38. This permits electricalconnections between substrate 20 and IPD zone 38 to be made even whenthe desired contact regions cannot for some other reason be verticallyaligned. An additional benefit of further interconnect layer 44 is thatlateral metallization regions may be provided therein to act as groundplanes or electrical shields or cross-unders or cross-overs or parts oftransmission lines or combinations thereof, where such functions areneeded. Since they are separated from the circuit being shielded ineither AD interconnect zone 26 and/or IPD zone 38 by substrate thickness31 and/or 35, they can have lower capacitance than if they were requiredto be a part of AD interconnect zone 26 and/or IPD zone 38 whereinter-level dielectric layers are much thinner than dimensions 31 and/or35. Thus, electromagnetic or RF circuit elements can be formed whereinone portion of the desired circuit element is formed in IPD zone 38 ofIPD chip 340′ and another portion of the desired circuit element isformed in further interconnect zone 44 of isolator chip 300′. Thevertical separation of the portions of such a circuit element thusincludes thickness 35 of IPD substrate 34′ and can be made greater thanis generally practical within an interconnection zone formed on a singlechip. For example, in an embodiment where the RF circuit element is atransmission line, one conductive strip of the transmission line can beformed in IPD zone 38 and a second conductive strip of the transmissionline formed in further interconnect zone 44. This pair of conductivestrips can be a differential signal pair or the conductive strip infurther interconnect zone 44, for example, can be a ground.

In another embodiment, for example, the RF circuit element can be aninductor having a patterned ground plane with the inductor loop(s) inIPD zone 38 and the patterned ground plane in further interconnect zone44, wherein the ground plane is patterned as is known in the art toreduce eddy current losses, and the relatively vertical distance 35between the inductor loop(s) in IPD zone 38 and the patterned groundplane in further interconnect zone 44 reduces the capacitance of this RFcircuit element. In a still further embodiment, for example, anelectromagnetic band gap structure (e.g., one or more tuned elements)can be formed in further interconnect zone 44 to enhance the shieldingof active device chip 200 and substrate 20 from stray electromagneticfields originating from a passive structure in IPD zone 38. A stilladditional advantage of further interconnect zone 44 is that it cansimplify the design of either or both of AD interconnect zone 26 and IPDzone 38 by providing a further level of conductive cross-unders orcross-overs or both, beyond those available within AD interconnect zone26 and/or IPD zone 38. For example, TSV 410 connects a contact (notshown) in IPD zone 38 to lateral conductor 47 in further interconnectzone 44, which is in turn connected to TSV 411 that returns to anothercontact (not shown) in IPD zone 38 in a location laterally displacedfrom TSV 410, thereby providing a cross-under. A cross-over, e.g., forAD interconnect zone 26, can be provided in an analogous manner.Accordingly, some of the TSVs intersecting further interconnect zone 44will pass through to TSVs in the next level vertically aligned therewith(e.g., 401, 402 and 406), while others can terminate (e.g., 408, 409,410, 411) on lateral connections, e.g., connections 46, 47, withinfurther interconnect zone 44 so that the conduction path to the next TSVis staggered (e.g., 408, 46, 409) or so that a cross-over or cross-under(e.g., 410, 47, 411) is formed. This combination of features greatlyincreases design flexibility. The foregoing are intended as non-limitingexamples of what can be accomplished by providing isolator chip 300′with further interconnect zone 44 thereon.

FIG. 3 is a simplified plan view of typical through-substrate-via (TSV)40 of diameter or width w employed in various embodiments of the presentinvention. While TSV 40 is shown in FIG. 3 as having a circular planview cross-section, this is merely for convenience of description andnot intended to be limiting and TSVs 40 can have any plan viewcross-sectional shape. Square, rectangular, polygonal, elliptical and soforth are non-limiting examples of other useful shapes. Region 50extending laterally outside of periphery 51 of TSV 40 is where variousinterconnections can be formed in IPD zone 38, further interconnect zone44 and/or AD interconnect zone 26. It is desirable for efficient circuitpacking that TSVs 40 have width w in the range of about 1 to 100micrometers more conveniently about 2 to 40 micrometers and preferablyabout 3 to 20 micrometers, and aspect ratios ARs of about 2:1 to 50:1,more conveniently about to 3:1 to 25:1 and preferably about 4:1 to 10:1if the conductive fill material is, for example, plated copper and about10:1 to 25:1 if the conductive fill material is, for example, chemicalvapor deposited (CVD) tungsten. In the case of TSVs having non-uniformcross-sections such as trenches or annular shapes, the smaller crosssection dimension is typically used in calculating the aspect ratioalthough it is recognized that the larger dimension in another directioncan enhance the ability to fill a TSV with a greater aspect ratio.Annular space 52 between TSV 40 and surrounding region 50 whereinterconnects or IPDs may be formed, should be wide enough to avoiddielectric breakdown and will depend upon the potentials that may beapplied to metal layers or IPDs within region 50 relative to TSV 40within periphery 51. This will depend upon the particular function beingperformed by 3-D IC 18 and is within the competence of persons of skillin the art.

FIGS. 4-16 are simplified schematic cross-sectional views of ageneralized wafer or chip in which through-substrate-via (TSV) 40 isbeing formed, during various stages of manufacture, according to stillfurther embodiments of the present invention. Referring now tomanufacturing stage 104 of FIG. 4, substrate 54 is provided havinginitial thickness 55 between upper surface 56 and lower surface 57.Substrate 54 represents any of substrates 20, 30, 30′, 34, 34′ of FIGS.1-2. IPD or interconnect zone 58 comprising dielectric layers 59 (e.g.,5 layers are illustrated) and metal layers 60 (e.g., 4 layers areillustrated) are formed on surface 56 of substrate 54 using means wellknown in the art. The number of dielectric layers 59 and metal layers 60will depend upon the particular electrical functions being implementedand may be larger or smaller than the numbers of layers illustrated inIPD or interconnect zone 58 of FIGS. 3-16. IPD or interconnect zone 58represents any or all of AD interconnect zone 26, further interconnectzone 44 if present and/or IPD zone 38. The details of such IPD orinterconnect zones are not represented, since they will depend upon theparticular circuit configuration and components being implemented.Suitable metals and dielectrics for layers 59 and 60 of interconnectzone 58 are well known in the art. Chemical-mechanical polishing (CMP)stop layer 62 is desirably provided above interconnect zone 58. Thisstop layer is intended to facilitate subsequent formation of the TSV.Silicon nitride with a thickness of at least about 200 to 1000nanometers is a non-limiting example of a suitable material for CMP stoplayer 62. CMP stop layer 62 is conveniently covered by hard mask layer64. Deposited silicon oxide of thickness at least of about 2 micrometersis suitable with about 2.4 micrometers thickness of TEOS formed siliconoxide being preferred, but thinner and thicker layers and othermaterials may also be used. Photoresist mask 66 having opening 67 ofwidth (e.g., diameter) 69 is provided above hard mask 64. Width 69 isconveniently slightly larger than finished TSV width w in order toaccommodate several thin liners desirably placed in the TSV cavitybefore filling it with metal. Structure 204 results.

Referring now to manufacturing stage 105 of FIG. 5, using masks 66, 64of FIG. 4, TSV cavity 70 is etched through IPD or interconnect zone 58to depth d′ below surface 56 in substrate 54. Depth d′ is slightlylarger than desired finished TSV depth d to accommodate the above-notedliners. Photo-resist mask 66 of FIG. 4 is conveniently used for etchingthrough layers 64, 62 and interconnect zone 58 using means well known inthe art depending upon the particular dielectric and metals usedtherein. Photoresist mask 66 is then conveniently removed in FIG. 5 andhard mask 64 used for etching cavity 70 in substrate 54. For siliconsubstrates, a plasma etch using alternating etch and polymer depositionsteps is a convenient procedure for anisotropic etching of siliconthrough hard mask 64. The plasma etcher preferably is of the inductivelycoupled plasma type, the etch step chemistry is based on SF₆, and thepolymerization step includes polymerizing gases such as C₄F₈ or CHF₃.However, other well known etch techniques can also be used. Depth d′ ischosen depending upon distances 21, 31, 35 needed in finished 3-D IC 18,18′ (see FIGS. 1-2) taking into account the relatively small thicknessof cavity liners described in connection with FIG. 6 and the aspectratio (AR) desired to be maintained. Structure 205 results.

Referring now to manufacturing stage 106 of FIG. 6, substantiallyconformal dielectric layer 72 is provided in cavity 70 and over mask 64.A sandwich of silicon oxide and silicon nitride is suitable, withsilicon nitride preferably having thicknesses about in the range of 20to 100 nanometers followed by silicon oxide of thickness about in therange of 100 to 1000 nanometers Plasma enhanced chemical vapordeposition (PECVD) is a convenient deposition method, but other layerformation methods well known in the art may also be used. Conformallayer 72 is followed by further substantially conformal layer 74comprising a barrier layer, preferably of a refractory material, ofabout 10 to 40 nanometers thickness. Layer 74 has upper surface 741.Where copper is intended to be used for filling TSVs 40 (e.g., byelectroplating), it often is desired to first deposit a seed layer ofcopper using sputtering or other deposition method to about 50 to 100nanometers thickness, and tantalum is a suitable barrier material. Wheretungsten is intended to be used for filling TSVs 40, titanium nitride ora combination of titanium nitride over titanium is a suitable barriermaterial. Other refractory barrier materials include tantalum nitride.Thinner or thicker layers and other materials can also be used.Structure 206 results.

Referring now to manufacturing stage 107 of FIG. 7, TSV cavity 70 isfilled with metal 76 by, for example, and not intended to be limiting,chemical vapor deposition (CVD), electroplating or a combinationthereof. For tungsten, CVD is suitable. For copper, electroplating issuitable, but other metals and layer formation techniques may also beused. The deposition process also provides portion 761 above layer 74.The thickness of the deposited metal should be sufficient to completelyfill TSV cavity 70. Structure 207 results which includes buried face 43of TSV 40. Referring now to manufacturing stage 108 of FIG. 8, excessmetal portion 761 above upper surface 741 of layer 74 is removed,generally by chemical-mechanical polishing (CMP). Additionally, in oneembodiment, the portions of layer 72 and the portions of hard mask 64that overlie the upper surface of CMP stop layer 62 are also removed.CMP stop layer 62 makes it possible to achieve a substantially planarsurface with exposed surface 41 of TSV 40 surrounded by a dielectricportion of IPD or interconnect zone 58, e.g., region 591 of dielectriclayers 59. Any remaining portions of CMP stop layer 62 may be removed byetching but in other embodiments can be left in place. In still furtherembodiments, if either layer 72 or hard mask 64 exhibits sufficient CMPstopping properties, then that layer may be sufficient to provide thedesired substantially planar surface and CMP stop layer 62 may beomitted. Structure 208 results. Referring now to manufacturing stage 109of FIG. 9, dielectric passivation layer 78 is applied covering surface41 of TSV 40 and surrounding dielectric regions 591 of IPD orinterconnect zone 58. Silicon oxi-nitride of a thickness of about 300 to700 nanometers is a suitable material and plasma enhanced chemical vapordeposition (PECVD) is a preferred formation means for forming layer 78,but other materials and larger or smaller thicknesses and otherformation techniques may also be used. Passivation layer 78 may includeone or more sub-layers. For example, and not intended to be limiting,passivation layer 78 can include a first layer of silicon nitride of 40to 100 nanometer thickness and a second layer of silicon oxide of 250 to600 nanometer thickness. Structure 209 results.

Manufacturing stages 110 through 112 of FIGS. 10-12 illustrate alternatemanufacturing stages depending upon the metallization pattern desired tobe deposited on surface 41 of TSV 40 and surrounding IPD or interconnectzone 58. In manufacturing stages 110A-112A of FIGS. 10A-12A, metal isdeposited only on surface 41 of TSV 40, while in manufacturing stages110B-112B of FIGS. 10B-12B, metal is deposited so as to couple surface41 of TSV 40 to a metal layer in IPD or interconnect zone 58 and toprovide other connection to one or more metal layers in IPD orinterconnect zone 58. Manufacturing stage 110A-112A; 110B-112B of FIGS.10A-12A and 10B-12B are described together since, other than the maskshapes provided, the steps are similar. Referring now to manufacturingstage 110A and 110B of FIGS. 10A and 10B, mask 80, 80′ is provided ondielectric layer 78 and openings 81, 81′, 81″ provided therein.Dielectric layer 78 is etched away beneath openings 81, 81′, 81″ toexpose underlying metal areas, e.g., surface 41 of TSV 40 and the uppersurfaces of metal layer portion 601, 602 in IPD or interconnect zone 58.In manufacturing stages 111A of FIG. 11A and 111B of FIG. 11B, metal 82is deposited so as to cover the metal surfaces exposed in mask openings81, 81′, 81″. Portions 822, 822′ of metal 82 overlie mask regions 80,80′ and portions 821, 821′, 823′ make contact with exposed metal surface41, and upper metal layer portions 601, 602 in IPD or interconnect zone58. Structures 211A, 211B result. Referring now to manufacturing stages112A of FIGS. 12A and 112B of FIG. 12B, mask portion 80, 80′ areremoved, thereby lifting off metal portions 822, 822′ leaving in FIG.12A, metal portion 821 on surface 41 of TSV 40, and in FIG. 12B metalportion 821′ on surface 41 of TSV 40 coupled to upper metal layerportion 601 to the left of TSV 40 in IDP or interconnect zone 58, andportion 823′ on another part of upper metal layer portion 602 in IDP orinterconnect zone 58 to the right of TSV 40 thereby illustrating thatconnections may be made to various portions of IDP or Interconnect zone58 during such manufacturing stage. Structures 212A, 212B result. Thismetallization method is commonly known as a lift-off process and may beselected for use with metals that are difficult to etch such as gold.Other metallization methods as are well known in the art may also beused to fabricate metal portions 821, 821′ and 823′ shown in FIGS. 12Aand 12B. In another embodiment, following deposition of passivationlayer 78 as in FIG. 9, mask layer 80 and 80′ are deposited andpatterned, followed by an etch to form openings 81, 81′, and 81″, indielectric layer 78 and portions of the upper dielectric region 591 toexpose the upper surface of conductive vias 40 and portions 601, 602 ofthe upper metal layer in IPD or interconnect zone 58 as shown in FIGS.10A and 10B. Mask regions 80 and 80′ are then removed. A layer of metal82 is deposited and patterned using photolithography and etching to formthe metal portions 821, 821′ and 823″ as shown in FIGS. 12A and 12B.Structures 212A, 212B result. This method of metallization is commonlyknown as a subtractive patterning process and is frequently used withaluminum metallization. In a still further embodiment, followingdeposition of passivation layer 78 as in FIG. 9, mask layer 80 and 80′are deposited and patterned, followed by an etch to form openings 81,81′, and 81″, in dielectric layer 78 and portions of the upperdielectric region 591 to expose upper surface 41 of conductive vias 40and portions 601, 602 of the upper metal layer in IPD or interconnectzone 58 as shown in FIGS. 10A and 10B. Mask layer regions 80 and 80′ arethen removed. A layer of metal 82 is deposited and patterned using aplanarizing CMP process to form the metal portions 821, 821′ and 823″ asshown in FIGS. 12A and 12B. Structures 212A, 212B result. This method ofmetallization is commonly known as an inlayed or damascene process. Thisembodiment is commonly used where it is desired that metal portions 821,821′, and 823′ comprise copper with a thickness of one micrometer orless. In yet another embodiment, following deposition of passivationlayer 78 as in FIG. 9, mask layer 80 and 80′ are deposited andpatterned, followed by an etch to form openings 81, 81′, and 81″, indielectric layer 78 and portions of the upper dielectric region 591 toexpose upper surface 41 of conductive vias 40 and portions 601, 602 ofthe upper metal layer in IPD or interconnect zone 58 as shown in FIGS.10A and 10B. Mask regions 80 and 80′ are then removed. A thinelectroplating metal seed layer is deposited (not shown) followed by theformation of a second mask layer (not shown) with openings having thedesired metal pattern with such openings to extend at least over theopenings 81, 81′, 81″. The patterned metal portions 821, 821′, and 823″are then formed by electroplating within the openings in the second masklayer using the electroplating metal seed layer as a plating electrode.Following the formation of metal portions 821, 821′, and 823′, thesecond mask layer is removed. Then the metal portions 821, 821′ and 823′are used as a hard mask in an etch process which removes the exposedportions of the thin electroplating metal seed layer while leaving theportions of the thin electroplating metal seed layer underlying themetal portions 821, 821′, and 823′. Structures 212A, 212B result. Thismethod of metallization is commonly known as plating through a mask.This embodiment can be especially beneficial where metal portions 821,821′ and 823′ are desirable formed of Cu with a thickness of greaterthan about 1 micrometer. Metal portions 821, 821′ and 823′ in any of theabove embodiments may include one or more diffusion barrier layers andmay also include an interface material to facilitate a subsequent 3-Dbonding process. In addition, while FIGS. 4-12 show the formation of TSV40 as passing thorough the previously formed IPD or interconnect zone58, TSV 40 can be fabricated following the deposition of the firstdielectric layer of IPD or interconnect zone 58. Subsequently, metallayers 60 and remaining dielectric layers of 59 of IPD or interconnectzone 58 are then formed over such TSV 40, and metal portion 821 thenformed over IPD or interconnect zone 58 with appropriate design suchthat metal portion 821 is electrically connected to such TSV 40. Any andall of these embodiments are useful.

Manufacturing stages 113, 114 of FIGS. 13-14 illustrate how presentlyburied surface 43 of TSV 40 is exposed and are substantially the same nomatter what pattern has been provided for metal 82. For economy ofillustration, only the “A” variety structure of FIG. 12A is illustratedin manufacturing stages 113-114 of FIGS. 13-14. Referring now tomanufacturing stage 113 of FIG. 13, structure 212A of FIG. 12 isinverted and attached to support 84 by adhesive 85. A variety of wellknown techniques may be used for mounting structure 212A (or 212B) onsupport 84 and a variety of materials used for support 84. Glass,ceramic, sapphire and semiconductor wafers are non-limiting examples ofmaterials suitable for support 84 and organic glues and double-sidedsticky tape are non-limiting examples of suitable materials for adhesive85. The preferred method utilizes glass wafers for support 84 and UVsensitive polymers for adhesive 85 as provided by 3M Electronic MarketsMaterials Division of the 3M Company of St. Paul, Minn. Structure 213results. Referring now to manufacturing stages 113 of FIG. 13 and 114 ofFIG. 14, the purpose of support 84 is to provide mechanical robustnessto wafer substrate 54 so that it can be thinned from initial thickness55 in FIG. 13 to final thickness of about depth d in FIG. 14 so thatburied face or surface 43 of TSV 40 is thereby exposed. Wafer substrate54 is preferably thinned by applying chemical-mechanical polishing(CMP), or a combination of grinding followed by CMP to rear surface 57of substrate 54 until portion 541 of substrate 54 has been removed toprovide thinned substrate 54′ on which formerly buried surface or face43 of TSV 40 is exposed. Other thinning techniques can also be used. Asshown in manufacturing stage 114 of FIG. 14, dielectric passivationlayer 86 with opening 87 is desirably applied to rear surface 57′ ofthinned substrate 54′ after CMP is complete. Surface 43 of TSV 40 isexposed in opening 87. In an illustrative embodiment, metal region 88 isformed in opening 87 in contact with surface 41 of TSV 40. Structure 214results. However, in other embodiments, dielectric passivation layer 86and/or metal region 88 may be omitted, depending upon whether substrate54, 54′ and the particular TSVs being formed therein will be part of ADsubstrate 20, isolator substrate 30 or IPD substrate 34, and the methodused for bonding IPD chip 34, isolator chip 300 and AD chip 200 togetherto form 3-D IC 18 and/or the method desired to mount 3-D IC 90, 18, 18′to a further circuit board, tape or substrate (not shown). Referring nowto manufacturing stages 115A, 115B of FIGS. 15A, 15B, support 84 andadhesive layer 85 are removed from thinned substrate 54′, the exactprocedure depending upon which adhesive system and support material havebeen chosen by the manufacturing process designer. In the preferredembodiment using the 3M provided system and materials, infra-redradiation projected through glass support 84 is used to soften adhesive85 so that thinned substrate 54′ with TSVs 40 may be lifted off, and anyremaining adhesive 85 may be pealed away. This can be accomplished whilethinned substrate 54′ is still in wafer form or after singulation whilestill attached to support 84. Either approach is useful. Structures 215Aor 215B result depending upon the lateral shape of mask 80, 80′ used inFIGS. 10A, 10B-11A, 11B.

Persons of skill in the art will understand based on the descriptionherein that even though FIGS. 3-15 show only a single TSV, that anynumber of TSVs 40 can be simultaneously fabricated using the illustratedmanufacturing stages in the same substrate at the same time. Further,substrates 54 can be different in both composition and thicknessdepending upon whether the particular wafer is intended to be an ADsubstrate 20 wafer with AD interconnect zone 26 thereon, or an isolatorsubstrate 30 wafer (with or without further interconnect zone 44thereon) or an IPD substrate 34 with IPD zone 38 thereon, but the TSVfabrication process, other than mask pattern changes, will besubstantially the same as that illustrated in FIGS. 3-15. Manufacturingstage 116 of FIG. 16 illustrates how different substrates 91, 92, 93fabricated according to FIGS. 3-15 can be stacked up and interconnectedto form 3-D IC 90 analogous to 3-D IC 18, 18′ of FIGS. 1-2 (but withoutthe interconnection detail). In FIG. 16, it is presumed that substrate91 and 92 in 3-D IC stack 90 are type B chips (see FIGS. 10B-12B and15B) and substrate 93 is a type A chip (see FIGS. 10A-12A and 15A), butthis is merely for convenience of illustration and persons of skill inthe art will understand that other metallization patterns can equallywell be used, with different variations in each of substrates 91, 92, 93of 3-D IC stack 90 using different IPD or interconnect zones 58-1, 58-2,58-3 in each substrate to suit the functions required of that level.Accordingly, the custom is adopted, as illustrated immediately above, ofadding the suffix -1, -2, -3 to various elements in the differentsubstrates 91, 92, 93 of the stack to indicate that their detailedlayout and arrangement can be different according to the function thateach level of 3-D IC 90 is performing. By way of example, the functionscorresponding to those shown in FIGS. 1-2 are indicated at the right ofFIG. 16 for each level.

Manufacturing stage 116 of FIG. 16 shows three substrates 91, 92, 93stacked one above the other and interconnected to form 3-D IC 90,corresponding to 3-D IC 18, 18′ of FIGS. 1-2. Substrate 91 correspondsto AD substrate 20 in combination with IPD or interconnect zone 58-1corresponding to AD interconnect zone 26. Substrate 91 has one or moreTSVs 40-1 of depth d-1 and width w-1 in thinned substrate 54′-1.Substrate 92 corresponds to isolator substrate 30 in combination withIPD or interconnect zone 58-2 corresponding to further interconnect zone44 if present. Substrate 92 has one or more TSVs 40-2 of depth d-2 andwidth w-2 in thinned substrate 54′-2. Substrate 93 corresponds to IPDsubstrate 34 in combination with IDP or interconnect zone 58-3corresponding to IPD zone 38. Substrate 93 has one or more TSVs 40-3 ofdepth d-3 and width w-3 in thinned substrate 54′-3. In this example,substrates 91, 92, 93 have mating TSVs 40-1, 40-2, 40-3, wherein metalportion 821′-1 and metal region 88-2 between substrates 91 and 92 coupleupper surface 41-1 of TSV 40-1 to metal region 88-2 on lower surface43-2 of TSV 40-2, and metal portion 821′-2 and metal region 88-3 betweensubstrates 92 and 93 couple upper surface 41-2 of TSV 40-2 to metalregion 88-3 on lower surface 43-3 of TSV 40-3. Metal portion 821-3 onupper surface 41-3 of TSV 40-3 is included to illustrate an externalbonding pad coupled to the stack of substrates 91, 92, 93 of 3-D IC 90.Surface 43-1 of lower TSV 40-1 with optional metal region 88-1 thereonis also exposed and thereby available to be coupled to an externalconnection such as, for example, a heat sink to facilitate heat removalfrom 3-D IC 90, or alternatively an additional electrical connection tothe 3-D IC 90. In another embodiment, if no electrical connections toTSV 40-1 in lower substrate 91 is desired, the formation of TSV 40-1 maybe omitted as a process simplification with metal portion 821′-1 coupledto AD interconnect zone 26. In another embodiment, electricalconnections of 3-D IC 90 can be by connections to the lower surface 43-1and/or metal region 88-1 of TSV 40-1 in lower substrate 91 rather thanto metal portion 821-3 of upper substrate 93. Either arrangement isuseful. Substrates 91, 92, 93 may be coupled in a variety of manners inorder to provide the inter-level connections illustrated in FIGS. 1-2and other desired connections. For example, if TSVs 40-1, 40-2, and 40-3and the metal portions 821′-1, 821′-2 (and/or metal portions 88-2, 88-3)are comprised of copper, the TSVs and metal portions can be electricallyand mechanically connected using a thermal-compression bonding processusing a temperature in the approximate range of 350° C. to 450° C., anda pressure of a few atmospheres for times in the approximate range of 15to 60 minutes. For example and not intended to be limiting, theinter-level connections may be formed by providing metal portions821′-1, 821′-2, 821-3 and/or metal portions 88 that include an interfacematerial to facilitate bonding as is well known in the art. For examplemetal portions 821′-1, 821′-2, 821-3 and/or 88-1, 88-2, 88-3 can beformed of copper with an interface material comprised of tin or indiumwhich would react with TSVs 40-1, 40-2, and 40-3 and the copper in themetal portion to form an intermetallic compound of copper and tin orcopper and indium during a thermal-compression bonding process. The useof the tin or indium interface material allows the thermal compressionbonding process to occur at reduced pressure, temperature, and/or timein comparison with the direct thermal-compression of copper-to-copperbonds. In another example, the interface material of 821-1, 821-2, 821-3and/or metal regions 88-1, 88-2, 88-3 can include a layer of a lowtemperature solder over a diffusion barrier layer. The use of a lowtemperature solder may further reduce the temperatures, times andpressures needed to achieve a bond in forming 3-D IC 90, 18, 18′,however the resulting bond may have reduced high temperature stabilityand weaker mechanical properties. In yet another example of use of abonding process known in the art, ultrasonic bonding may be used withmaterials such as gold. Metal portions 821′-1, 821′-2, and 821-3 and/or88-1, 88-2, 88-3 can be comprised of gold, or be formed of another metalwith an interface material which includes a gold layer over a diffusionbarrier layer. Likewise TSVs 40-1, 40-2, and 40-3 can have a diffusionbarrier and gold interface layer, such as for example, metal regions88-1, 88-2, 88-3 formed over surfaces 43-1, 43-2, and 43-3. Substrates91, 92, 93 in either wafer or chip form can be aligned and bonded usingeither a sequential bonding processes or a simultaneous bondingprocesses, as are well known in the art. For example, in a usefulprocess, wafer-to-wafer bonding using copper-to-copper or copper/tinthermal-compression bonding can be used to first align and bondsubstrate 92 to substrate 91, and then subsequently bond substrate 93 tocombined substrates 92 and 91. In another useful process using solderinterface materials in a chip-to-chip or chip-to-wafer bonding,substrate 92 can be aligned and held in place on substrate 91 using atemporary bond material, followed by placing substrate 93 over substrate92, and then heating to simultaneously fuse all of TSVs 40 to theirmating TSVs or contacts to the IPDs or interconnect metallization of thedifferent levels. Where AD substrate 20 is very thin, for example withthickness 21 in the range of about 10-20 micrometers or less, it isdesirable but not essential that bonding of 3-D IC stack 90 be performedbefore very thin AD substrate 20 is released from support 84. This canbe accomplished while substrate 20 is still in wafer form and attachedto support 84 and chips 300 and 340 have been singulated and are bondedto substrate 20 still in wafer form attached to support 84 and thensubstrate 20 with chips 300, 340 attached is singulated to provide 3-DICs 90, 18, 18′. Alternatively, substrate 200 can be singulated alongwith support 84 while still attached thereto. Then chips 200, 300, 340can be bonded together to form 3-D IC 90, 18′, 18′ and then thesingulated portions of support 84 removed from stacked and bonded chips200, 300, 340. Any and all of these alternative means and methods andcombinations thereof may be used to form 3-D IC 90, 18, 18′. Structure216 results.

In the forgoing discussion it has been assumed that AD chips 200,isolator chips 300 and IPD chips 343 are formed on separate substratesand then stacked and bonded together before or after singulation or acombination thereof. This is a preferred method. However, in a furtherembodiment that is especially applicable when isolator substrate 30 andIPD substrate 34 can have common physical properties (e.g., similarresistivity and thickness) isolator chips 300 and IPD chips 340 may beformed at the same time in different locations on the same substrate,wherein a first portion of the substrate is used for isolator chips 300and another portion of the same substrate is used for IPD chips 340. Thechips or the two different regions of the common substrate are thensingulated or separated and combined with AD chips 200 or AD substrate20 to form 3-D IC 90, 18, 18′. Where IPD zone 38 and furtherinterconnect region 44 involve multilayer dielectric-metal structuresemploying similar and/or compatible materials, such combined fabricationis useful. Accordingly, as used herein, the terms “separately formed”and “separately fabricated” and “fabricated (or formed) on separatesubstrates” are intended to include the variation described here whereisolator chips 300 and IPD chips 340 are formed in different locationson a common substrate before singulation or separation.

It will be further recognized that, while the 3-D ICs have beendescribed herein as comprising AD chip 200, isolator chip 300 and IPDchip 340; the present invention applies to other combinations of chipsand other chip functions. For example, IPD chip 340 may comprise otherelements, passive and/or active, besides integrated passive devices,where it is desired to reduce electromagnetic coupling between devices,conductors, elements or regions on chip 340 and devices, conductors,elements or regions on chip 200 by providing isolator chip 300therebetween. Accordingly, the terms “integrated passive devices” andthe abbreviation “IPD” are intended to include other electronic elementsand not be limited merely to passive devices alone, although that is notprecluded. Thus, in its broadest sense, the terms “chip 340”, “chip(340)”, “IPD chip” and “IPD chip 340” or equivalents are intended toinclude chips with any arrangement of active devices alone, passivedevices alone and any combinations of active and passive devices. Thus,IPD zone 38 is not limited merely to include passive devices but mayinclude multilayer metal-dielectric structures or other elements for anypurpose and may be referred to as “interconnect zone 38”. In thesituation where chip 340 is made up of active devices, it can be formedin different regions of a common substrate with the active devices of ADchip 200. Accordingly, in this situation, the terms “separately formed”and “separately fabricated” and “fabricated (or formed) on separatesubstrates” as used herein are also intended to include the variationdescribed here where IPD chips 340 or third chips 340 and AD chips 200are formed in different locations on a common substrate beforesingulation or separation and stacking.

According to a first embodiment, there is provided a 3-D integratedcircuit (IC) (90, 18, 18′), comprising, an active device (AD) substrate(20) having an AD region (26) thereon with device contacts therein, anisolator substrate (30), separately formed from the AD substrate (20)and having one or more through-substrate-vias (TSVs) (4030) thereinadapted to be coupled to one or more of the device contacts in the ADregion (26) of the AD substrate (20), and an integrated passive device(IPD) substrate (34), separately formed from the AD substrate (20) andthe isolator substrate (30) and having an IPD zone (38) on its surfacein which IPDs have been formed, and having one or more TSVs (4034) therethrough, adapted to couple one or more of the IPDs in the IPD zone (38)to TSVs (4030) in the isolator substrate (30). According to a furtherembodiment, at least some of the TSVs (4030) in the isolator substrate(30) are coupled to some of the device contacts in the AD region (26) onthe AD Substrate (20). According to a still further embodiment, the ICcomprises a further interconnect zone (44) located between the secondisolator substrate (30) and the third IPD substrate (34). According to ayet further embodiment, some of the device contacts on the AD substrate(20) are coupled to other device contacts on the AD substrate (20) viathe further interconnect zone (44). According to a still yet furtherembodiment, some of the IPDs are coupled to other of the IPDs via thefurther interconnect zone (44). According to a yet still furtherembodiment, at least one of the IPDs has a first element located in theIPD zone (38) and a second element located in the further interconnectzone (44). According to another embodiment, the isolator substrate (30)has a resistivity of a 1000 ohm-cm or greater. According to a stillanother embodiment, the isolator substrate (30) has a thickness in therange of about 10 and 200 micrometers or larger. According to a yetanother embodiment, the IPD substrate (34) has a resistivity of a 1000ohm-cm or greater. According to a still yet another embodiment, theisolator substrate (30) has a thickness in the range of about 10 and 200micrometers or larger. According to a yet still another embodiment, theAD substrate (20) has a first thickness (21), the isolator substrate(30) has a second thickness (31) and the IPD substrate (34) has a thirdthickness (35), and at least one or both of the second (31) and thirdthickness (35) are at least about 2-20 times the first thickness (21).

According to a second embodiment, there is provided a method for forminga 3-D integrated circuit (IC) (90, 18, 18′), comprising, forming onseparate substrates (20, 30, 34) at least an active device chip (200),an isolator chip (300) and an integrated passive device (IPD) chip(340), wherein at least two of such chips (200, 300, 340) have one ormore conductor filled vias (40) extending there through and wherein atleast some vias in the IPD chip (340) are coupled to one or moreintegrated components on the IPD chip (340), stacking the active devicechip (200), the isolator chip (300) and the IPD chip (340) so that afirst via in a first of the at least two chips is aligned with a secondvia in another of the at least two chips; and bonding the active devicechip (200), the isolator chip (300) and the integrated passive device(IPD) chip (340) together so that the first and second vias areelectrically coupled. According to a further embodiment, the formingstep comprises, forming the active device chip (200), the isolator chip(300) and the IPD chip (340) with one or more levels of interconnects(26, 44, 38) on first surfaces thereof, some of which are coupled duringthe bonding step with one or more vias (40) exposed on a rear face of achip to which it is being bonded in the bonding step. According to astill further embodiment, the forming step comprises, providing aninitial substrate (54) having a front face (56) and a rear face (57),etching a blind via cavity (70) in the initial substrate (54) extendingfrom the front face (56) toward the rear face (57), filling the blindcavity (70) with a conductor (76) having an interior surface (43)proximate a bottom of the cavity (70), removing excess conductor (761)from above the blind cavity (70) to expose a first face (41) of theconductor (76) filling the blind cavity (70), mounting the substrate(54) on a support (84) with the first face (41) toward the support (84),removing material from the rear face (57) of the initial substrate (54)thereby providing a thinned substrate (54′) having therein a conductorfilled via (40) of depth d extending there through and with the firstface (41) and the interior surface (43) of the conductor (76) in thecavity (70) exposed, and removing the support (84) from the thinnedsubstrate (54′). According to yet further embodiment, the method furthercomprises providing an interconnect zone (58) on the front face (56) ofthe initial substrate (54), and wherein the step of removing excessconductor (761) comprises removing excess conductor (761) over theinterconnect zone (58).

According to a third embodiment, there is provided a 3-D integratedcircuit (IC), comprising, an active device chip (200) formed on anactive device substrate (20) having an active device interconnect zone(26, 58-1) on a first face (22, 56-1) thereof and one or more firstconductor filled vias (4020, 40-1) extending from the first face (22,56-1) to an opposite second face (23, 57-1) thereof, an isolator chip(300) formed on an isolator substrate (30) having a further interconnectzone (44, 58-2) on a first face (32, 56-2) thereof coupled to one ormore second conductor filled vias (4030, 4030′, 40-2) extending from thefirst face (32, 56-2) to an opposite second face (33, 57′-2) thereof, athird chip (340) containing integrated passive devices or other elementsor both formed on a third substrate (34) and having an interconnect zone(38, 58-3) on a first face (36, 56-3) thereof coupled to one or morethird conductor filled vias (4034, 4034′, 40-3) extending from the firstface (36, 56-3) to an opposite second face (37, 57′-3) thereof, andwherein the active device chip (200), the isolator chip (300) and thirdchip (340) are bonded together so that at least some of the thirdconductor filled vias (4034, 4034′, 40-3) are coupled to at least someof the second conductor filled vias (4030, 4030′, 40-2). According to afurther embodiment, at least some of the second conductor filled vias(4030, 4030′, 40-2) are coupled to one or more of the first conductorfilled vias (4020, 40-1). According to a still further embodiment, theactive device interconnect zone (26, 58-1) on the active device chip(200) couples at least one of the active devices on the active devicechip (200) to one or more of the first conductor filled vias (4020,40-1).

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention, it being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims and their legal equivalents.

What is claimed is:
 1. A method for forming a 3-D integrated circuit, comprising: forming an active device (AD) substrate having an AD region thereon with device contacts therein; forming an isolator substrate separately from the AD substrate and having one or more through-substrate-vias (TSVs) therein adapted to be coupled to one or more of the device contacts in the AD region of the AD substrate; forming an integrated passive device (IPD) substrate separately from the AD substrate and the isolator substrate and having an IPD zone on its surface in which IPDs have been formed, and having a plurality of TSVs formed underlying the IPD zone through the IPD substrate, wherein the TSVs in the IPD substrate are coupled with the IPDs in the IPD zone, and at least some of the TSVs are adapted to couple one or more of the IPDs in the IPD zone to TSVs in the isolator substrate, and wherein at least some of the TSVs in the isolator substrate are vertically aligned with at least some of the TSVs in the IPD substrate; and forming a further interconnect zone located between the isolator substrate and the IPD substrate, wherein the further interconnect zone includes a lateral conductor between two or more TSVs in a same substrate, thereby providing a connection selected from a group consisting of a cross-under connection between two or more IPDs in the IPD zone, and a cross-over connection between two or more device contacts of the AD substrate, and wherein at least one of the IPDs has a first element located in the IPD zone and a second element located in the further interconnect zone.
 2. The method of claim 1, wherein at least some of the TSVs in the isolator substrate are coupled to some of the device contacts in the AD region on the AD substrate.
 3. The method of claim 1, wherein some of the IPDs are coupled to other of the IPDs via the further interconnect zone.
 4. The method of claim 1, wherein the isolator substrate has a resistivity of 1000 ohm-cm or greater.
 5. The method of claim 1, wherein the isolator substrate has a thickness in a range of 10 and 200 micrometers or larger.
 6. The method of claim 1, wherein the IPD substrate has a resistivity of 1000 ohm-cm or greater.
 7. The method of claim 1, wherein the AD substrate has a first thickness, the isolator substrate has a second thickness, and the IPD substrate has a third thickness, and at least one or both of the second and third thickness are at least 2-20 times the first thickness.
 8. The method of claim 1, wherein the further interconnect zone includes an additional portion selected from a ground plane, and electrical shield, and an electromagnetic band gap structure.
 9. The method of claim 1, further comprising a circuit element, wherein a first portion of the circuit element is formed in the IPD zone, and a second portion of the circuit element is formed in the further interconnect zone, and wherein the circuit element is selected from an RF transmission line with first and second conductive strips, and an inductor with an inductor loop and a patterned ground plane.
 10. A method of forming a 3-D integrated circuit, comprising: forming an active device (AD) substrate having an AD region thereon with device contacts therein; forming an isolator substrate separately from the AD substrate and having one or more through-substrate-vias (TSVs) therein adapted to be coupled to one or more of the device contacts in the AD region of the AD substrate; forming an integrated passive device (IPD) substrate separately from the AD substrate and the isolator substrate and having an IPD zone on its surface in which IPDs have been formed, and having a plurality of TSVs formed underlying the IPD zone through the IPD substrate, wherein the TSVs in the IPD substrate are coupled with the IPDs in the IPD zone, and at least some of the TSVs are adapted to couple one or more of the IPDs in the IPD zone to TSVs in the isolator substrate; forming a further interconnect zone located between the isolator substrate and the IPD substrate, wherein the further interconnect zone includes a lateral conductor between two or more TSVs in the IPD substrate, thereby providing a cross-under connection between two or more IPDs in the IPD zone; and forming a circuit element, wherein a first portion of the circuit element is formed in the IPD zone, and a second portion of the circuit element is formed in the further interconnect zone.
 11. The method of claim 10, wherein the further interconnect zone includes a ground plane.
 12. The method of claim 10, wherein the further interconnect zone includes an electrical shield.
 13. The method of claim 10, wherein the further interconnect zone includes an electromagnetic band gap structure having one or more tuned elements.
 14. The method of claim 10, wherein the circuit element is an RF transmission line, the first portion of the circuit element is a first conductive strip of the RF transmission line, and the second portion of the circuit element is a second conductive strip of the RF transmission line.
 15. The method of claim 14, wherein the first conductive strip and the second conductive strip form a differential signal pair.
 16. The method of claim 14, wherein the second conductive strip is a ground.
 17. The method of claim 10, wherein the circuit element is an inductor, the first portion of the circuit element is an inductor loop, and the second portion is a patterned ground plane. 